Various downhole gauges and memory tools are known for obtaining data relating to the downhole conditions in a borehole. Previously, these gauges were largely mechanical or electromechanical tools used to measure such conditions as downhole pressure and temperature. More recently, these gauges have tended to be primarily electronic tools utilizing downhole microprocessors which either transmit the downhole data to the surface for analysis or store such downhole data in the tool for subsequent retrieval and analysis at the surface.
Various examples of self-contained downhole measurement systems or gauges, which store the data therein for subsequent retrieval and analysis at the surface, are provided by U.S. Pat. No. 4,033,186 issued Jul. 5, 1977 to Bresie, U.S. Pat. No. 4,161,782 issued Jul. 17, 1979 to McCracken and reissued on Apr. 26, 1983 as U.S. Pat. No. Re. 31,222, U.S. Pat. No. 4,593,370 issued Jun. 3, 1986 to Balkani, U.S. Pat. No. 4,665,398 issued May 12, 1987 to Lynch et. al., U.S. Pat. No. 4,709,234 issued Nov. 24, 1987 to Forehand et. al., U.S. Pat. No. 4,715,002 issued Dec. 22, 1987 to Vernon et. al., U.S. Pat. No. 4,866,607 issued Sep. 12, 1989 to Anderson et. al., U.S. Pat. No. 5,153,832 issued Oct. 6, 1992 to Anderson et. al. and U.S. Pat. No. 5,337,234 issued Aug. 9, 1994 to Anderson et. al.
More particularly, the apparatus of Bresie is specifically designed for use in sensing downhole conditions in an oil well drill hole, and more particularly, for measuring pressure and temperature conditions within the oil well drill hole, to assist in directing the drilling operation. The drilling operation ceases and the self-contained apparatus of Bresie is lowered into the drilling hole suspended from a line, such as a wire, cable or pipe, to the desired depth. Following the recording of the downhole data in the drilling hole, the apparatus is removed from the drilling hole and the downhole data is retrieved at the surface for analysis. The drilling operation is then resumed.
Similarly, Lynch et. al., Forehand et. al., and each Anderson et. al. relate to a method or self-contained downhole gauge disposed in a wellbore for sampling and recording information pertaining to a physical condition in the wellbore. The self-contained downhole gauge is described as being disposed in the wellbore by a suitable hoisting or tool carrier means of a type as known to the art. More particularly, by way of example, the suitable known hoisting or carrier means are described to be a wireline or a drill string which is raised and lowered in the wellbore by draw works and traveling block as known to the art.
Vernon et. al. also describes the use of a measuring sonde for recording a variable value or measurement in a producing petroleum well as a function of a parameter such as time. The measurement sonde is lowered into the producing well suspended at the end of a simple wireline or a cable which goes through the wellhead at the surface and runs over a return pulley and winds on a winch. This arrangement makes it possible to move the sonde in the well by reeling or unreeling the wireline or cable.
The above-described mechanism for transporting or conveying the measurement apparatus, gauge or sonde within the wellbore may be unsatisfactory for some applications or uses, such as for the measurement of downhole conditions in a production well. For instance, the use of a wireline or cable typically requires specialized equipment, such as a wireline truck, and specialized personnel trained in its use. The need for specialized equipment and personnel may increase the time and cost associated with placing the measurement apparatus, obtaining the measurements and subsequently removing the apparatus. Further, production from the wellbore may need to be terminated during the taking of the measurements by the apparatus.
Thus, there is a need in the industry for a device for sensing and recording downhole data relating to an ambient environment in a production well and a method for obtaining such downhole data utilizing the device. Further, there is a need for such a device which may be installed in and removed from the production well without the need for specialized equipment or personnel as described above.